The present invention relates to an adaptive shunt system for controlling the structural, vibrations, and more specifically, to an adaptive shunt system for adaptively controlling the structural vibrations from frequency-varying structures as a command voltage calculated in real time by estimated natural frequency of the frequency-varying structures is fed thereto, and method therefor
Generally, the shunt system is for controlling the vibrations of the frequency-varying structures. Namely, the shunt system suppresses a vibration occurred in the systems, such as the space structures, sports articles (including snow boards and tennis rackets), and ultra-high precision machines (including the precision optical instruments and the semiconductor manufacturing equipment).
FIG. 1 is a circuit diagram showing the conventional passive shunt circuit.
As shown in FIG. 1, the conventional passive shunt circuit comprises an inductance unit 200 including two operation-amplifiers 220A and 220B, a power supply 400, and a mechanical-to-electrical conversion unit 100.
The mechanical-to-electrical conversion unit 100 performs as a capacitor 120 for converting the vibration energy of a structure to electrical energies. Therefore, the conventional passive shunt circuit forms a L-R-C circuit as inductance unit 200, the capacitor 120 of the mechanical-to-electrical conversion unit 100 and a variable resistor R0 between the mechanical-to-electrical conversion unit 100 and the inductance unit 200 are serially connected.
This conventional passive shunt circuit has been used to control the vibrations of structures, but in this circuit, as the vibration frequencies of the structure are varied, so its performance is drastically degraded.
FIG. 2 illustrates the graphs showing the frequency response results of the uncontrolled cases and the results of the controlled cases using the conventional passive circuit of FIG. 1. As shown in the graphs, as the vibration frequency is diminished from F0 to F1 and F2, the vibration control performance is drastically degraded.
Other conventional methods for controlling the vibrations of structures will be explained below.
First, of the methods, there is a method in which a motor is used to change a resistance of the circuit and to cope with the vibration frequency of the structure. Therefore, the vibration controlling system adopting the motor has disadvantages in that it consumes a lot of power and its size and weight are also increased.
Second, there is another method adopting a PLL circuit. The PLL circuit searches and locks the vibration frequency of a single mode. However, the vibrating controlling system adopting the PLL circuit has disadvantage in that it can not detect the vibration frequency not only at an excessive vibration response, but also in multiple modes.
Third, there is still another method adjusting a amount of oil within a tuned-mass-damper. Namely, the system adjusts the rigidity of structures as a motor varies the natural frequency of a tank. However, the system using the above method can not be easily installed and further its installation expense is high.
Fourth, there is further method adopting a piezoelectric device. For example, a gyroscope using the piezoelectric device precisely measure the outer angular velocity. However, because it consists of a complicated circuit and adopts an algorithm for controlling it, the configuration cost of the system is high. Therefore, the system is applicable only to the expensive system.
FIG. 3A illustrates graphs showing frequency responses when the center frequency of the passive shunt circuit of FIG. 1 shifts. FIG. 3B illustrates graphs showing frequency responses when the electrical damping ratio of the passive shunt of FIG. 1 shifts.
As shown in the drawings, the tuning characteristics of the conventional passive shunt are quite sensitively varied with respect to the variations of the vibration frequencies. Thus, it can be seen that the vibration characteristics are steeply shifted when the electrical center frequencyshifts. Also, the overlapping of the frequency response at the points S1 and T1 are the same as predicted theoretically, which gives an indirect proof that the experiment was accurate to us.
It is an object of the present invention to provide an adaptive shunt system for adaptively controlling the structural vibrations from the frequency-varying structures as command voltage calculated in realtime by estimated natural frequency of the frequency-varying structures is fed thereto, and method therefor.
It is another object of the present invention to provide an adaptive shunt for controlling the vibrations of a structure, and an operating method for the same, in which the vibration frequencies as estimated in a DSP board on a real time basis are made to have an electrical center frequency suiting to the vibration frequencies of the structure, thereby controlling the vibrations of the structure.
In order to achieve the objects of the present invention, there is provide to an adaptive shunt system for controlling vibrations of a frequency-varying structure, the system comprising: a detector 700 for detecting vibrations generated from a predetermined structure and generating vibration signals corresponding to the vibrations; a computer 600 for inputting the vibrations signals from the detector; a signal processing unit 500 for processing the vibration signals from the computer and generating a voltage command in real-time; and an adaptive shunt device 900 for adaptively controlling the vibrations of the structure of which natural frequency varies at every moment according to the voltage command.
In order to achieve the another objects of the present invention, there is provide to a vibration controlling method of a structure which varies its natural frequency, the method comprising the steps of: detecting vibrations generated from the structure; estimating a target model based on the detected vibrations; calculating vibration frequencies based on the estimated target model; adjusting a command voltage if the vibration frequencies converge to real frequencies of the structure; and controlling the vibrations of the structure according to the command voltage.